Zinc toxicity

Background

• Transition metal
• Essential nutrient
• Exposure from diet, medicinal uses, nutritional supplements, and occupational exposures
  • Multiple case reports of zinc toxicity related to ingestion of United States pennies which contain 97.5% zinc

Toxicokinetics

• Absorbed primarily in the jejunum
• Excreted via the GI tract with minimal amounts excreted in the urine
• Accumulates in erythrocytes
  • Whole blood concentrations are 6-7x higher than in the serum
• Inverse relationship with copper
  • Excess zinc absorption will cause a counterregulatory response resulting in copper elimination

Clinical Features

Acute

• GI distress
  • Nausea
  • Vomiting
  • Abdominal pain
  • GI bleeding
  • Partial and full thickness burns causing strictures with zinc chloride solutions with >20% zinc
• Inhalation
  • Lacrimation
  • Rhinitis
  • Dyspnea
  • Acute lung injury
  • Acute Respiratory Distress Syndrome
  • Metal fume fever

Chronic

• Zinc induced copper deficiency
  • Reversible sideroblastic anemia
  • Reversible myelodysplastic syndrome
• Progressive myeloneuropathy
  • Spastic gait
  • Sensory ataxia

Background

Heavy metal toxicity results from exposure to metals like lead, mercury, arsenic, or cadmium, which interfere with cellular function. Exposure may occur occupationally, environmentally, through ingestion, or from alternative medicines. Chronic toxicity can present insidiously, while acute toxicity may mimic sepsis or encephalopathy. Diagnosis is often delayed due to nonspecific symptoms.

Clinical Features

Symptoms depend on the metal and exposure duration but may include:

Neurologic: Peripheral neuropathy, confusion, tremor, encephalopathy

GI: Abdominal pain, nausea, vomiting, diarrhea, anorexia

Heme: Anemia (especially microcytic or hemolytic), basophilic stippling (lead)

Renal: Tubular dysfunction, proteinuria, Fanconi syndrome

Dermatologic: Mees’ lines (arsenic), hyperpigmentation, hair loss

Others: Fatigue, weight loss, hypertension (cadmium), immunosuppression

Differential Diagnosis

Sepsis or systemic inflammatory response

Drug toxicity or overdose

Metabolic disorders (e.g., porphyria, uremia)

Psychiatric illness (if symptoms are vague or bizarre)

Neurologic diseases (e.g., Guillain-Barré, MS, Parkinson’s)

Vitamin deficiencies (e.g., B12, thiamine)

Evaluation

Workup

History: Occupational exposures, home remedies, hobbies (e.g., jewelry making, battery recycling), diet, water source, imported goods

Labs:

• CBC, CMP, urinalysis
• Blood lead level, serum/urine arsenic, mercury, or cadmium (based on suspicion)
• Urine heavy metal screen (note: spot testing may require creatinine correction)

Imaging: Abdominal X-ray (radiopaque material in GI tract, especially with lead)

EKG: Evaluate for QT prolongation or arrhythmias in severe cases

Diagnosis

Confirmed by elevated blood or urine levels of the specific metal in the context of clinical findings. Hair and nail testing are unreliable for acute toxicity. Interpret results with toxicologist input if possible.

Management

Remove the source of exposure (e.g., occupational control, GI decontamination if recent ingestion)

Supportive care: IV fluids, seizure control, electrolyte repletion

Chelation therapy (in consultation with toxicology or Poison Control):

Lead: EDTA, dimercaprol (BAL), succimer

Mercury/arsenic: Dimercaprol or DMSA

Cadmium: No effective chelation—focus on supportive care

Notify local public health authorities if exposure source is environmental or occupational

Disposition

Admit if symptomatic, unstable, or requiring chelation

Discharge may be appropriate for asymptomatic patients with low-level exposure and outpatient follow-up

Arrange toxicology or environmental medicine follow-up for source control and serial testing

See Also

• Aluminum toxicity
• Antimony toxicity
• Arsenic toxicity
• Barium toxicity
• Bismuth toxicity
• Cadmium toxicity
• Chromium toxicity
• Cobalt toxicity
• Copper toxicity
• Gold toxicity
• Iron toxicity
• Lead toxicity
• Lithium toxicity
• Manganese toxicity
• Mercury toxicity
• Nickel toxicity
• Phosphorus toxicity
• Platinum toxicity
• Selenium toxicity
• Silver toxicity
• Thallium toxicity
• Tin toxicity
• Zinc toxicity

Evaluation

• BMP
• CBC
• Copper level
• Ceruloplasmin level
• Abdominal films to assess for foreign bodies
• MRI
  • Will show increase T₂ signal in the dorsal columns of the cervical cord

Management

• Oral toxicity
  • Supportive Care
    • Hydration
    • H₂ receptor antagonists or PPI
    • Antiemetics
  • Consider whole bowel irrigation
• Inhalation
  • Supportive care
    • Oxygen therapy
    • Bronchodilators
  • Metal fume fever
    • Usually self limiting
    • CXR usually normal
• Chelation
  • Limited data on use, and data present is based off of case reports and treatment for lead toxicity
  • Consider in patients with hemodynamic compromise
  • CaNa₂EDTA, British antilewisite, DTPA were all successfully used in case reports
  • 1000mg/m²/d IV CaNa₂EDTA every 6 hours
    • Based on a successful case report, but should be given in conjunction with toxicology or poison control center
• Dermal Exposures
  • Do not use water in metallic zinc exposures
    • Concern metal will ignite
  • Remove zinc with forceps and apply mineral oil to affected skin
• Copper replacement
  • Oral copper alone shown to improve hematopoietic effects and prevent further neurological deterioration

Disposition

• Consult Toxicology or poison control